Re: ATM off axis newtonians.

[Anthony Stillman <atmer@flash.net>]

Sam Michael wrote:
>...a 12 newtonian...with a mask that covered up the majority
>of the mirror save a 4" diameter hole towards one edge.
>...Does this trick/gimick really do anything?


Compared to a 4" obstructed Newtonian, the off-axis masked scope will
provide better contrast.  It isn't really fair to compare it to an APO, as
the APO doesn't have two mirrors scattering light.

If you have a lot of light (the Moon, the planets), it can be fun to play
with apodizing masks.  I think the square ones are the most interesting,
given their curious transfer properties.


Sam Michael wrote:
>Is there a way to set up a simulation of this in oslo?

Yes.

In the "Surface Data" Window, in the "Aperture Radius" column, click the
box associated with the surface you want to mask.  Select "Special Aperture
Data" (X) in the drop down menu.  This will open a window in which you can
choose the shape of the mask (here an ellipse), its size and position.  The
Y axis is up and down.  The X axis it right and left.  I like to render the
3D drawing to make sure I put it where I think I put it.


Ken Lowther is misquoted as writing:
>...a physics professor at a...party...off the top of his head...
>...seemed pretty sure of himself.

Those physics profs sure know how to party.


Anthony


PS  Ken, seriously, I think the point spread function does a good job of
showing the effect of an obstruction.